Does the smoothness of the sliding surface affect friction? Explain.

Friction is caused by the irregularities on the two surfaces in contact. Even those surfaces which appear very smooth have a large number of minute irregularities on them. Irregularities on the two surfaces lock into one another. When we attempt to move any one surface over other, we have to apply a force to overcome interlocking. On rough surface, there are a large number of irregularities. So the force of friction is greater if a rough surface is involved.